1. Field of the Invention
The present invention relates to fasteners and threaded nuts. More particularly, the present invention relates to low profile slotted spanner locknuts having at least two spanner slots.
2. Background of the Invention
Conventional fasteners include bolts in combination with nuts. The most common nuts have a multi-faceted outer edge, and can be easily installed or removed with commonly available wrenches and sockets. When easy removal is not desired, however, nuts having a rounded outer edge are often used to discourage tampering or adjustment. A key of some sort is provided for installation or adjustment with a specially designed tool.
A low profile is sometimes desirable for rounded nuts, for appearance purposes and to make undesired removal or adjustment more difficult. However, low profile nuts have fewer threads, making lasting engagement with a bolt more difficult to achieve. For this and perhaps other reasons including to prevent loosening, a nylon or other plastic insert is sometimes used with such low profile nuts, to lock its position after installation. Nuts which have such inserts are commonly called locknuts. Keyed, low profile locknuts are used in many applications because they are tamper resistant.
The key in low profile locknuts can include spaced opposing orifices which span the center of the locknut. Such nuts are called spanner locknuts. Spanner drives having projections which fit in the orifices are used to install spanner locknuts.
Locknuts have also been manufactured which contain a single slot on the outside edge for installation with a specifically adapted installation tool. Such locknuts are generally not intended to be reusable and discourage easy adjustment. However, installation of single slot spanner locknuts is difficult to automate and can result in an unbalanced torque loading condition when the locknut is seated. Furthermore, single slot locknuts allow a relatively low degree of angularity between the tool and the axis of the nut during installation, and substantial rotation of the installation tool is sometimes needed to engage the tool with the nut.
Thus, there is a need for low-profile, effective and cosmetic locknuts which can be easily and efficiently adjusted after installation, which provide balanced load conditions, and which can be re-used, if desired. There is also a need for tamper resistant slotted locknuts which allow a relatively high degree of angularity between the installation tool and the nut, and do not require substantial rotation of the tool to engage the nut.